A

• Aachen
• Aaron
• Abaddon
• Abandonment
• Abarim
• Abba
• Abbacy Nullius of Wettingen-Mehrerau
• Abbate Giuseppe Baini
• Abbe
• Abbess
• Abbey
• Abbey and Congregation of Melk
• Abbey and Diocese of Bobbio
• Abbey and School of Clonmacnoise
• Abbey of Arbroath
• Abbey of Barlings
• Abbey of Bec
• Abbey of Benedictbeurn
• Abbey of Citeaux
• Abbey of Clairvaux
• Abbey of Cornillon
• Abbey of Corvey
• Abbey of Croyland
• Abbey of Deer
• Abbey of Dissentis
• Abbey of Dorchester
• Abbey of Dundrennan
• Abbey of Dunfermline
• Abbey of Echternach
• Abbey of Einsiedeln
• Abbey of Engelberg
• Abbey of Farfa
• Abbey of Ferrieres
• Abbey of Flavigny
• Abbey of Fleury
• Abbey of Floreffe
• Abbey of Fontenelle
• Abbey of Frigolet
• Abbey of Gottweig
• Abbey of Grottaferrata
• Abbey of Hirschau
• Abbey of Lehnin
• Abbey of Lerins
• Abbey of Leubus
• Abbey of Luxeuil
• Abbey of Mellifont
• Abbey of Melrose
• Abbey of Miridite
• Abbey of Monte Cassino
• Abbey of Morimond
• Abbey of Newhouse
• Abbey of Our Lady of Gethsemani
• Abbey of Pontigny
• Abbey of Rievaulx
• Abbey of Saint Albans
• Abbey of Saint Augustine
• Abbey of Saint Remy
• Abbey of Saint Vaast
• Abbey of Saint-Denis
• Abbey of Saint-Ouen
• Abbey of Saint-Victor
• Abbey of Sainte-Genevieve
• Abbey of Savigny
• Abbey of St. Emmeram
• Abbey of St. Gall
• Abbey of St. Solesmes
• Abbey of Strahov
• Abbey of the Park
• Abbey of Tongerloo
• Abbey of Trinita di Cava Dei Tirreni
• Abbey of Vadstena
• Abbey of Waldsassen
• Abbey of Whitby
• Abbo Cernuus
• Abbot
• Abbreviators
• Abdera
• Abdias
• Abdias of Babylon
• Abdication
• Abduction
• Abecedaria
• Abecedarians
• Abel (Place Name)
• Abel (Son of Adam)
• Abenakis
• Aberdeen
• Abiathar
• Abila
• Abipones
• Abisai
• Abjuration
• Abner
• Abortion
• Abraham
• Abraham (In Liturgy)
• Abraham a Sancta Clara
• Abraham Ecchelensis
• Abraham Janssens
• Abraham Ortelius
• Abraham van Diepenbeeck
• Abraham Woodhead
• Abraham-Ben-Meir Aben-Ezra
• Abrahamites
• Abrasax
• Absalom
• Absalon of Lund
• Absinthe
• Absolution
• Abstemii
• Abstinence
• Abstraction
• Abthain
• Abundius
• Abydus
• Abyss
• Abyssinia
• Acacia
• Acacius (Bishop of Beroea)
• Acacius (Bishop of Caesarea in Palestine)
• Acacius (Patriarch of Constantinople)
• Acadia
• Acanthus (Plant)
• Acanthus (Titular See)
• Acathistus (Akathistos)
• Accaron
• Accentus Ecclesiasticus
• Acceptance
• Acceptants
• Accession
• Accessus
• Acciajuoli
• Accident
• Acclamation
• Acclamation (In Papal Elections)
• Accomplice
• Accusations of Treason
• Acephali
• Acerenza
• Achab
• Achaia
• Achaicus
• Achard de Saint-Victor
• Achaz
• Achiacharus
• Achille Desurmont
• Achille Gagliardi
• Achimaas
• Achimelech
• Achitopel
• Achonry
• Achor Valley
• Achrida
• Aci-Reale
• Acmonia
• Acoemetae
• Acolouthia
• Acolyte
• Acquapendente
• Acquaviva (Cardinals)
• Acqui
• Acre
• Acrostic
• Act of Settlement (Irish)
• Acta Pilati
• Acta Sanctae Sedis
• Acta Sanctorum Hiberniae
• Acta Triadis Thaumaturgae
• Acts of Roman Congregations
• Acts of the Apostles
• Acts of the Martyrs
• Actual Grace
• Actus Et Potentia
• Actus Primus
• Actus Purus
• Acuas
• Ad Apostolicae Dignitatis Apicem
• Ad Limina Apostolorum
• Ad Sanctam Beati Petri Sedem
• Ad Universalis Ecclesiae
• Adalbert
• Adalbert I
• Adalbert Stifter
• Adam
• Adam Blackwood
• Adam Contzen
• Adam de Marisco
• Adam Easton
• Adam Franz Lennig
• Adam Heinrich Mueller
• Adam in Early Christian Liturgy and Literature
• Adam Krafft
• Adam Mickiewicz
• Adam of Bremen
• Adam of Fulda
• Adam of Murimuth
• Adam of Perseigne
• Adam of St. Victor
• Adam of Usk
• Adam Scotus
• Adam Tanner
• Adamites
• Adana
• Adar
• Addas
• Adelaide
• Adelaide Anne Procter
• Adelard of Bath
• Adele Amalie Gallitzin
• Adele Bayer
• Adelmann
• Adelophagi
• Adeodatus
• Adeste Fidelis
• Adjuration
• Administrator
• Administrator (Of Church Property)
• Admiral Sands (Benjamin and James)
• Admont
• Adolf Pfister
• Adolphe Dechamps
• Adolphe Perraud
• Adolphe-Napoleon Didron
• Adolphus von Dalberg
• Adonai
• Adonias
• Adoption
• Adoptionism
• Adoration
• Adoro Te Devote
• Adria
• Adrian and Peter von Walenburch
• Adrian Hamsted
• Adrian of Castello
• Adrian Turnebus
• Adrian Willaert
• Adrianople
• Adrien Baillet
• Adrien Greslon
• Adrien Rouquette
• Adso
• Adullam
• Adulteration of Food
• Adultery
• Advent
• Adventists
• Advocates of Roman Congregations
• Advocates of St. Peter
• Advocatus Diaboli
• Advocatus Ecclesiae
• Advowson
• Adytum
• Aedh of Kildare
• Aegidius of Viterbo
• Aelfric, Abbot of Eynsham
• Aelia Flaccilla
• Aelnoth
• Aenas of Gaza
• Aeneas McDonnell Dawson
• Aenon
• Aeons
• Aer
• Aeris of Pontus
• Aesthetics
• Aeterni Patris
• Aeterni Patris
• Aetius
• Affinity (In Canon Law)
• Affinity (In the Bible)
• Affirmation
• Afflighem
• Afonzo de Albuquerque
• Africa
• African Liturgy
• African Synods
• Agabus
• Agape
• Agapetae
• Agapetus
• Agathangelus
• Agathias
• Agaunum
• Age of Reason
• Agen
• Agents of Roman Congregations
• Aggeus (Haggai)
• Agios O Theos
• Agnes Mary Clerke
• Agnetz
• Agnoetae
• Agnolo, Giovanni, and Taddeo Gaddi
• Agnosticism
• Agnus Dei
• Agnus Dei (In Liturgy)
• Agonistici
• Agony of Christ
• Agostini Agazzari
• Agostino Barbosa
• Agostino Bernal
• Agostino Ciasca
• Agostino Steffani
• Agostino Steuco
• Agra
• Agram (Zagreb)
• Agrapha
• Agrarianism
• Agria
• Agrippinus
• Aguas Calientes
• Agustin Quintana
• Ahicam
• Ahriman and Ormuzd
• Aire
• Aisle
• Aistulph
• Aix
• Ajaccio
• Akhmin
• Alabama
• Alabanda
• Alabaster
• Alagoas
• Alain Chartier
• Alain de l'Isle
• Alain-Rene Le Sage
• Alalis
• Alan of Tewkesbury
• Alan of Walsingham
• Alanus de Rupe (Alanus de la Roche)
• Alaska
• Alatri
• Alb
• Alba Pompeia
• Alban Butler
• Alban Isidor Stolz
• Albanenses
• Albani
• Albania
• Albano
• Albany
• Albenga
• Alberic of Monte Cassino
• Alberic of Ostia
• Alberico de Rosate
• Albero de Montreuil
• Albert (Albrecht), Bishop of Riga
• Albert (Jean) Belin
• Albert Anton von Muchar
• Albert Auguste de Lapparent
• Albert II
• Albert Knoll
• Albert of Aachen
• Albert of Brandenburg
• Albert of Castile
• Albert of Saxony
• Albert of Stade
• Albert Pighius
• Albert Stoeckl
• Albert Vandal
• Albert von Behaim
• Alberto Arnoldi
• Albi (Albia)
• Albigenses
• Albinus
• Albrecht Durer
• Albrecht von Eyb
• Albrecht von Wallenstein
• Alchemy
• Alcimus
• Alcoholism
• Alcuin
• Aldersbach
• Aldfrith
• Aldus Manutius
• Alejandro Herculano de Carvalho e Araujo
• Aleppo
• Ales and Terralba
• Alessandria Della Paglia
• Alessandro Bonvicino
• Alessandro Farnese
• Alessandro Manzoni
• Alessandro Piccolomini
• Alessandro Scarlatti
• Alessandro Serpieri
• Alessandro Tassoni
• Alessandro Volta
• Alessio
• Alesso Baldovinetti
• Alexander (Early Bishops)
• Alexander (Name of Seven Men)
• Alexander Agricola
• Alexander Baumgartner
• Alexander Bicknor
• Alexander Goss
• Alexander Hegius
• Alexander Hohenlohe-Waldenburg-Schillingsfuerst
• Alexander Kaufmann
• Alexander MacDonell
• Alexander Martin Sullivan
• Alexander Maximilian Seitz
• Alexander Natalis
• Alexander of Abonoteichos
• Alexander of Hales
• Alexander of Lycopolis
• Alexander of Neckam
• Alexander Pope
• Alexander Severus
• Alexander V
• Alexandre de Prouville, Marquis de Tracy
• Alexandre de Rhodes
• Alexandre Guy Pingre
• Alexandre Rodrigues Ferreira
• Alexandre Vincent Jandel
• Alexandre-Antonin Tache
• Alexandre-Etienne Choron
• Alexandria
• Alexandria
• Alexian Nuns
• Alexians
• Alexis de Tocqueville
• Alexis John Augustine Bachelot
• Alexis-Francois Artaud de Montor
• Alexis-Francois Rio
• Alexis-Paulin Paris
• Alexis-Xyste Bernard
• Alfonso Capecelatro
• Alfonso de Valdes
• Alfonso de Zamora
• Alfonso Muzzarelli
• Alfonso of Burgos
• Alfred Rethel
• Alfred the Great
• Alfred von Reumont
• Alfred-Henri-Amand-Mame
• Alger of Liege
• Alghero
• Algiers
• Algonquins
• Alife
• Alimentation
• Alimony
• Aliturgical Days
• All Hallows College
• All Saints' Day
• All Souls' Day
• Allah
• Allahabad
• Alleluia
• Allesandro Galilei
• Allocution
• Allori
• Alma
• Alma Redemptoris Mater
• Almeria
• Alms and Almsgiving
• Alogi
• Aloisio Gardellini
• Aloisius Lilius
• Aloisius-Edouard-Camille Gaultier
• Alonso Andrada
• Alonso Berruguete
• Alonso Cano
• Alonso de Ercilla y Zuniga
• Alonso de Espinosa
• Alonso de Ojeda
• Alonso Rodriguez
• Alonso Tostado
• Alonzo Coello Sanchez
• Alonzo de Alvarado
• Alonzo de Barcena
• Alonzo Sanchez
• Aloys Karl Ohler
• Aloys Lutolf
• Aloys Senefelder
• Aloysius Bellecius
• Aloysius Gentili
• Aloysius Schlor
• Aloysius Taparelli
• Alpha and Omega
• Alpha and Omega (In Scripture)
• Alphabetic Psalms
• Alphons Huber
• Alphonse de Lamartine
• Alphonse Magnien
• Alphonso de Spina
• Alphonsus de Castro
• Alsace-Lorraine
• Altamura and Acquaviva
• Altar (In Liturgy)
• Altar Bell
• Altar Breadboxes
• Altar Breads
• Altar Candles
• Altar Candlesticks
• Altar Canopy
• Altar Cards
• Altar Carpets
• Altar Cavity
• Altar Cloths
• Altar Crucifix
• Altar Curtain
• Altar Frontal
• Altar Horns
• Altar Lamp
• Altar Lanterns
• Altar Ledge
• Altar Linens
• Altar of Our Lady
• Altar of Repose
• Altar Protector
• Altar Rail
• Altar Screen
• Altar Side
• Altar Steps
• Altar Stole
• Altar Stone
• Altar Tomb
• Altar Vase
• Altar Vessels
• Altar Wine
• Altarage
• Altarpiece
• Altars (In Scripture)
• Altars (In the Greek Churches)
• Alton (Illinois)
• Altoona
• Altruism
• Alumnus
• Alvar Nunez Cabeza de Vaca
• Alvarez Carillo Gil de Albornoz
• Alvarez de Paz
• Alvaro Alonzo Barba
• Alvaro de Mendana de Neyra
• Alvarus Pelagius
• Ama
• Amadia and Akra
• Amalarius of Metz
• Amalec (Amalek)
• Amalfi
• Amalricians
• Amalricus Augerii
• Amasia
• Amastris
• Amathus
• Amazones
• Ambition
• Ambo
• Ambo (In the Russian and Greek Church)
• Ambrogio Borgognone
• Ambrogio Calepino
• Ambrogio Foppa
• Ambroise Pare
• Ambrose Autpert
• Ambrose Bernard O'Higgins
• Ambrose Corbie
• Ambrose Lisle March Phillipps de Lisle
• Ambrose Marechal
• Ambrose Pelargus
• Ambrose Saint-John
• Ambrosian Basilica
• Ambrosian Chant
• Ambrosian Hymnography
• Ambrosian Library
• Ambrosian Liturgy and Rite
• Ambrosians
• Ambrosiaster
• Ambrosio Morales
• Ambulatory
• Amelia
• Amen
• Amende Honorable
• America
• American Federation of Catholic Societies
• American Indians
• Amerigo Vespucci
• Amice
• Amida
• Amiel Weeks Whipple
• Amiens
• Amisus
• Ammon
• Ammonian Sections
• Ammonites
• Amorbach
• Amorios
• Amorrhites
• Amos
• Amovibility
• Amoy
• Ampere
• Amphilochius of Iconium
• Amphilochius of Sida
• Amphorae
• Ampullae
• Ampurias
• Amra
• Amrah
• Amraphel
• Amsterdam
• Amulet
• Amyclae
• Anabaptists
• Anacletus II
• Anaesthesia
• Anagni
• Analogy
• Analysis
• Anaphora
• Anarchy
• Anastasiopolis
• Anastasius Bibliothecarius
• Anastasius Grun
• Anathema
• Anathoth
• Anatole de Bengy
• Anatole Leroy-Beaulieu
• Anatomy
• Anazarbus
• Anchorites
• Ancient Diocese and Monastery of Lindisfarne
• Ancient Diocese of Bristol
• Ancient Diocese of Chester
• Ancient Diocese of Hereford
• Ancient Diocese of Macon
• Ancient Diocese of Norwich
• Ancient Diocese of Saint Asaph
• Ancient Diocese of Sodor and Man
• Ancient Diocese of Vaison
• Ancient Diocese of Worcester
• Ancient of Days
• Ancient Order of Hibernians
• Ancient See of Aarhus in Denmark
• Ancient See of Bergen in Norway
• Ancient See of Borglum
• Ancient See of Odense
• Ancient See of Oslo
• Ancient See of Ribe in Denmark (Jutland)
• Ancient See of Roskilde in Denmark
• Ancient See of Skara
• Ancient See of Stavanger
• Ancient See of Strengnas
• Ancient See of Trondhjem
• Ancient See of Vexio
• Ancient See of Viborg in Denmark
• Ancient See of Westeraas
• Ancient See of Winchester
• Ancient See of York
• Ancilla Dei
• Ancona and Umana
• Ancren Riwle
• Ancyra
• Andalusia
• Andechs
• Andras Medulic
• Andre Dacier
• Andre de Boulanger
• Andre Garin
• Andre Guijon
• Andre Terrason
• Andre-Hercule de Fleury
• Andre-Jean Cuoq
• Andrea Adami Da Bolsena
• Andrea Alciati
• Andrea Borromeo
• Andrea Castagno
• Andrea Cesalpino
• Andrea Ciccione
• Andrea Contucci Del Sansovino
• Andrea Del Sarto
• Andrea Del Verrocchio
• Andrea Della Robbia
• Andrea Doria
• Andrea Gallandi
• Andrea Mantegna
• Andrea Palladio
• Andrea Pisano
• Andrea Spagni
• Andrea Vanni
• Andreas Agnellus of Ravenna
• Andreas Benedict Feilmoser
• Andreas de Vega
• Andreas Hofer
• Andreas Kobler
• Andreas of Ratisbon
• Andreas Pozzo
• Andreas Rass
• Andreas Vesalius
• Andres Cavo
• Andres Perez de Ribas
• Andres Urdaneta
• Andrew Byrne
• Andrew Donlevy
• Andrew Foreman
• Andrew Gordon
• Andrew Krzycki
• Andrew of Caesarea
• Andrew of Lonjumeau
• Andrew of Rhodes
• Andrew of Wyntoun
• Andrew White
• Andria
• Anemurium
• Ange de Saint Joseph
• Ange de Sainte Rosalie
• Angel de Saavedra Remirez de Baquedano
• Angelica Kauffman
• Angelique Bullion
• Angelo Clareno Da Cingoli
• Angelo Mai
• Angelo Maria Quirini
• Angelo Rocca
• Angelo Secchi
• Angels
• Angels of the Churches
• Angelus
• Angelus Bell
• Anger
• Angers
• Anglican Orders
• Anglicanism
• Anglona-Tursi
• Angola and Congo
• Angora
• Angouleme
• Angra
• Anhalt
• Anima Christi
• Animals in Christian Art
• Animals in the Bible
• Animism
• Anise
• Ann Lobera
• Anna
• Anna Comnena
• Annals of the Four Masters
• Annas
• Annates
• Anne Dacier
• Anne Garcia
• Anne Hanson Dorsey
• Anne, First Duke of Montmorency
• Anne-Madeleine Remuzat
• Anne-Robert-Jacques Turgot
• Anne-Therese Guerin
• Annecy
• Annibale d'Annibaldi
• Annius of Viterbo
• Ansegisus (Archbishop of Sens)
• Anselm Eckart
• Anselm of Laon
• Anselm of Liege
• Anselmo Banduri
• Antediluvians
• Anthemius
• Anthon Rafael Mengs
• Anthony Blanc
• Anthony Brookby
• Anthony Champney
• Anthony Daniel
• Anthony Koberger
• Anthony Konings
• Anthony Maria Anderledy
• Anthony of Sienna
• Anthony of the Mother of God
• Anthony Parkinson
• Anthony Rey
• Anthony Terill (Bonville)
• Anthropomorphism
• Antichrist
• Antidicomarianites
• Antidoron
• Antigonish
• Antimensium
• Antinoe
• Antinomianism
• Antioch
• Antiochene Liturgy
• Antiochus of Palestine
• Antipater of Bostra
• Antipatris
• Antiphellos
• Antiphon
• Antiphon (in Greek Liturgy)
• Antiphon (In the Greek Church)
• Antiphonary
• Antiphonary of Bangor
• Antipodes
• Antipope
• Antipope John XVI (XVII)
• Antipope John XXIII
• Antiquity of the World
• Antivari
• Antofogaste
• Antoine and Guillaume Duprat
• Antoine Anselme
• Antoine d'Abbadie
• Antoine de Gaudier
• Antoine de Lamothe, Sieur de Cadillac
• Antoine de Mouchy
• Antoine de Ulloa
• Antoine Galland
• Antoine Gaubil
• Antoine Godeau
• Antoine Henri de Berault-Bercastel
• Antoine Massoulie
• Antoine Pagi
• Antoine Perrenot de Granvelle
• Antoine Touron
• Antoine-Augustin Parmentier
• Antoine-Augustin Touttee
• Antoine-Cesar Becquerel
• Antoine-Dominique Magaud
• Antoine-Elisabeth Dareste de la Chavanne
• Antoine-Frederic Ozanam
• Antoine-Joseph Mege
• Antoine-Laurent Lavoisier
• Antoine-Lefebvre, Sieur de la Barre
• Antoine-Leonard de Chezy
• Antoine-Simon Maillard
• Anton Berlage
• Anton Brus
• Anton Dereser
• Anton Guenther
• Anton Joseph Binterim
• Anton Martin Slomsek
• Anton Sander
• Anton Ulrich
• Antonello da Messina
• Antonino Diana
• Antoninus Pius
• Antonio Allegri
• Antonio Amico
• Antonio and Piero Benci Pollajuolo
• Antonio Aparisi y Guijarro
• Antonio Ballerini
• Antonio Bosio
• Antonio Canova
• Antonio Comellas y Cluet
• Antonio Da Fonseca Soares
• Antonio de Alcedo
• Antonio de Andrada
• Antonio de Araujo
• Antonio de Herrera y Tordesillas
• Antonio de Molina
• Antonio de Trueba
• Antonio di Matteo di Domenico Rosselino
• Antonio Escobar y Mendoza
• Antonio Espejo
• Antonio Fernandez
• Antonio Ferreira
• Antonio Francesco Vezzosi
• Antonio Lotti
• Antonio Magliabechi
• Antonio Margil
• Antonio Martini
• Antonio Montesino
• Antonio Neri
• Antonio Ravalli
• Antonio Ruiz de Montoya
• Antonio Stradivari
• Antonio Tebaldeo
• Antonio Vieira
• Antonis van Dashort Mor
• Antonius
• Antonius Augustinus
• Antonius Fischer
• Antonius Possevinus
• Antony Hickey O.F.M.
• Antony Kohlmann
• Antoon (Anthonis) van Dyck
• Antwerp
• Aosta
• Apaches
• Apameia
• Apelles
• Aphraates
• Apiarius of Sicca
• Apocalypse
• Apocatastasis
• Apocrisiarius
• Apocrypha
• Apocrypha (Notes)
• Apodosis
• Apollinarianism
• Apollinaris (The Elder)
• Apollonius of Ephesus
• Apologetics
• Apolysis
• Apolytikion
• Apophthegmata
• Aporti
• Apostasy
• Apostle (In Liturgy)
• Apostle Spoons
• Apostles
• Apostles' Creed
• Apostolic Blessing
• Apostolic Camera
• Apostolic Canons
• Apostolic Church-Ordinance
• Apostolic Churches
• Apostolic College
• Apostolic Constitutions
• Apostolic Examiners
• Apostolic Executor
• Apostolic Expeditors
• Apostolic Indulgences
• Apostolic Letters
• Apostolic Majesty
• Apostolic Schools
• Apostolic Succession
• Apostolic Syndic
• Apostolicae Curae
• Apostolicae Sedis Moderationi
• Apostolicae Servitutis
• Apostolici
• Apostolici Ministerii
• Apostolici Regiminis
• Apostolicity
• Apostolicum Pascendi Minis
• Apotactics
• Apotheosis
• Apparitor
• Appeal As From An Abuse
• Appeals
• Appetite
• Approbation
• Appropriation
• Apse
• Apse Chapel
• Apsidiole
• Aquarians
• Aquila
• Aquila and Priscilla
• Aquileia
• Aquileian Rite
• Aquino, Sora, and Pontecorvo
• Arabia
• Arabian School of Philosophy
• Arabici
• Arabissus
• Arad
• Arason Jon
• Arator
• Araucania
• Araucanians
• Arawaks
• Arbitration
• Arca
• Arcadiopolis
• Arcae
• Arcanum
• Arch
• Archaeology
• Archaeology of the Cross and Crucifix
• Archange de Lyon
• Archbishop
• Archconfraternity
• Archconfraternity of Holy Agony
• Archconfraternity of the Holy Family
• Archconfraternity of the Most Precious Blood
• Archdeacon
• Archdiocese
• Archelais
• Archiereus
• Archimandrite
• Archontics
• Archpriest
• Archpriest Controversy
• Arcosolium
• Arculf
• Ardagh
• Ardbraccan
• Ardo Smaragdus
• Areopolis
• Arequipa
• Arethas of Caesarea
• Arethusa
• Arezzo
• Argentina
• Argos
• Argyll and the Isles
• Arianism
• Ariano
• Ariassus
• Aribo
• Arindela
• Aristaces Azaria
• Aristeas
• Aristides
• Aristotle
• Arius
• Arizona
• Ark of the Covenant
• Arkansas
• Armagh
• Armand David
• Armand de La Richardie
• Armand-Benjamin Caillau
• Armand-Hippolyte-Louis Fizeau
• Armella Nicolas
• Armenia
• Armenierstadt
• Armidale
• Arminianism
• Arnaldus Villanovanus
• Arnaud d'Ossat
• Arnauld
• Arni Thorlaksson
• Arnobius
• Arnold
• Arnold Forster
• Arnold Ipolyi
• Arnold Janssen
• Arnold of Brescia
• Arnold Pannartz and Konrad Sweinheim
• Arnolfo di Cambio
• Arnulf of Bavaria
• Arnulf of Lisieux
• Arras
• Arsacidae
• Arsenius Autorianos
• Arsinoe
• Artemon
• Arthur Bell
• Arthur Moore
• Arthur O'Leary
• Arthur-Marie Le Hir
• Arthur-Richard Dillon
• Articles of Faith
• Artoklasia
• Artvin
• Arundell (Family)
• Ascalon
• Ascelin
• Ascendente Domino
• Ascension
• Ascetical Theology
• Asceticism
• Ascoli, Satriano, and Cirignola
• Ascoli-Piceno
• Aseity
• Aseneth
• Aser
• Asgaard
• Ash Wednesday
• Ashes
• Asia
• Asia Minor
• Asiongaber (Ezion-Geber)
• Asmodeus
• Aspendus
• Asperges
• Assam
• Assemani
• Assemblies of the French Clergy
• Assessor of the Holy Office
• Assessors
• Assideans
• Assisi
• Assistant at the Pontifical Throne
• Assistant Priest
• Assizes of Jerusalem
• Association of Ideas
• Association of Priestly Perseverance
• Association of the Holy Childhood
• Assuerus
• Assumption of Mary
• Assur
• Assur
• Assyria
• Asterisk
• Asterius
• Asti
• Aston
• Astorga
• Astrology
• Astronomy
• Astronomy in the Bible
• Asylums and Care For the Insane
• Atahuallpa
• Atavism
• Athanasius Kircher
• Atheism
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• St. Adalbert
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• St. Afra
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• St. Anastasius
• St. Anastasius Sinaita
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• St. Anatolius
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• St. Andrew
• St. Andrew Avellino
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• St. Anselm of Lucca, the Younger
• St. Anthony
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• St. Apollinaris Claudius
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• The Athanasian Creed
• The Augustinus-Verein
• The Authorized Version
• The Avesta